Java Web Start Faq's - General Questions

What is Java Web Start?
Java Web Start provides a platform-independent, secure, and robust deployment technology. It enables developers to deploy full-featured applications to end-users by making the applications available on a standard web server. With any web browser, end-users can launch the applications and be confident they always have the most-recent version.

Where do I get more information?
Look at the online documentation for Java Web Start .
If you are a developer, go to the Developer's Guide for detailed technical information on how to deploy applications using Java Web Start.

Why should I use Java Web Start?
It's an easy, robust, and secure way to deploy applications directly from the web. Developers can make applications readily available via the web. In addition, Java Web Start provides Java runtime environment (JRE) management capabilities, it's easy to set up, it's browser-independent, and it's an efficient way to deploy web application solutions.
Users can easily access applications much as they would a web page--without a separate installation step. From the desktop, users can access and use Java applications, using a richer and more responsive user interface than is available on a web page. And, once a Java Web Start based application is installed, users simply click to run the application whenever needed.
Users do not need to manually update applications because each time they launch an application, it is transparently updated from the web--so they always use the most recent version available.

How can I launch applications with Java Web Start?
You initially launch a new application by clicking on a link from a web page.
If you use an application frequently, create a shortcut from your desktop or from the Start Menu by allowing Java Web Start to place an icon on your desktop. Java Web Start may ask if you would like to create
shortcuts or an entry in the Start Menu. If you say "yes," all future launches of the application can start without a browser.
Java Web Start also provides an Application Cache Viewer which you can launch from the Java Control Panel. The Cache Viewer enables you to directly launch applications you have downloaded.
You can also launch an application from a command prompt by typing “javaws ” where Does it matter how I launch an application?
No, applications launch in the same manner no matter which method you use: from a web page, from the shortcut on the desktop, from the Start menu, or through the Java Application Cache Viewer.
Java Web Start always checks to see if a newer version of the application is available for use and automatically downloads it if so.
If the application you are using has not been digitally signed, Java Web Start will launch it in a restricted and secure execution environment. An application that is not signed, or one that you do not trust, will never be run with unrestricted access to your local system or network.

What are the system requirements for Java Web Start?
Any client system that supports the Java version 1.2.2 or higher can use Java Web Start. Java Web Start works with virtually all browsers.

What platforms does Java Web Start run on?
Sun Microsystems provides versions for Windows 98/NT/2000/XP/2003, Solaris Operating Environment (SPARC and Intel editions) and Linux/i486. Apple provides a version for their OS X release.

What are the server requirements for Java Web Start?
Java Web Start uses HTTP for communication between the client and the server. You can use a standard web server to host an application. If you require additional services, such as version-based downloading, incremental updates, or pack200 compression for your applications, the web server will need to support servlets or Java Server Pages. A sample servlet implementing these features is provided in the samples directory of the JDK.

Is Java Web Start based on a standard?
Yes. Java Web Start 1.5.0 is the product-quality reference implementation of Java Network Launching Protocol (JNLP) technology, which was developed through the Java Community Process. JNLP is specification number JSR 056. Other platform vendors are encouraged to port Java Web Start to their platform or implement the specification.
For more information, see the JNLP specification.

Can I implement my own Java Web Start?
The underlying technology for Java Web Start, the Java Network Launching Protocol and API is being developed through the Java Community Process, so you can implement this protocol in any product. However additional licensing and terms must be met to implement any JCP technology including the JNLP technology.

What are the supported browsers?
Java Web Start supports primarily Internet Explorer 4 or higher and Mozilla. However any browser can launch JNLP files if you have set the MIME-type association correctly. Java Web Start uses the browser's settings and may launch a browser to show a URL; this feature may not work with unsupported browsers.

Can I deploy any application with Java Web Start?
Java Web Start is an application launcher for Java applications that are written to be web-deployed.
An application must be delivered in a set of JAR files and all application resources, such as images, configuration files, and native libraries must be included in the JAR files. The resources must be looked up using the method ClassLoader.getResource() or an equivalent method. Java Web Start only transfers JAR files from the web server to the client.
If an application is written to run in a restricted execution environment (sandbox), then access to disk is not permitted and the application may only connect to the host on which it resides.

Is Java Web Start a software distribution mechanism like Marimba and MS SMS?
Java Web Start is an application launcher for Java applications. It allows easy distribution of full-featured applications based on the Java platform from a web server to a client machine with minimal user interaction.
The software distribution technology is only one aspect of Java Web Start. It also provides security, updates to the applications, ease-of-use for end users, and flexibility for developers when they create the applications.

Is Java Web Start an application installer?
Java Web Start is an application launcher for Java applications that are written to be web-deployed. Java Web Start caches resources locally on the disk, but also provides a secure execution environment and a virtually transparent updating facility for applications. The end user does not need to manually initiate a software update because the application is updated each time it is used.

What version of the Java platform does Java Web Start work with?
Java Web Start launches only applications written for the Java platform versions 1.2.2 and higher.

How does Java Web Start relate to Java Plug-in Technology (applets)?
The two approaches are very similar. The key difference is in the user experience. If the Java application/applet needs to interact with a web page and be tightly bound to a web browser, then applets may be the solution. On the other hand, if browser independence is important, then Java Web Start is the deployment platform of choice. There are a number of other differences, but this is the fundamental difference.
Java Plug-in technology enables users to run Java applets inside a browser.
Java Web Start enables users to download full-featured applications with any browser. Once they have downloaded and launched an application, the browser can be closed, while the application continues working. The application does not depend on an open browser to function. The browser can be shut down or you can go to a different web page and the application will continue running.